1 SUMITOMO KAGAKU 2008- I Introduction With the goal of providing food for the human race as well as having a stable food supply at present and in the future, agricultural chemicals (i.e. pesticides) are being disseminated as economically effective methods for preventing reduced yields in crops due to damage by insects and weeds. The pesticides are roughly divid- ed from their targets into insecticides which include insect growth regulators for exterminating harmful insects, fungicides for preventing and eliminating fungi such as powdery mildew affecting the growth of plants, and herbicides which include plant growth regulators for preventing weeds, and each of them has a superior efficacy for organisms that are harmful to crops. These pesticides are intentionally applied outdoors to agricul- tural land, so in addition to the efficacy of pesticides for various diseases and insects that damage crops (bene- fit), evaluations of their impact not only on the health of farmers and consumers but also wild animals (risk) are necessary in determining their usefulness as pesti- cides. There is a long history of safety evaluations based on various types of toxicity tests using mammals from the standpoint of assuring the health of humans, but there has been an increase in the awareness of environmental protection recently, and evaluations of the effects of pesticides on the environment, including wild animals, have become indispensable for develop- ment of new pesticides and maintaining the registra- tion of existing chemicals already on the market. How- ever, there is a wide variety of wild animal species to be evaluated, and just among the vertebrates alone, there are various types including mammals, birds, reptiles, amphibians and fish. In addition, the diversity of their ecology and shortage of information on life history of some species make it very difficult to evaluate the safe- ty for individual species. Incidentally, since the pesti- cides that are applied to cultivated land are considered to enter the hydrosphere of the rivers and lakes adja- cent to the cultivated fields with the movement of air and rain as they undergo various types of metabolism and decomposition, the evaluation of the environmental impacts of pesticides on the ecosystem of the hydros- phere is one of the most important areas in evaluations of safety. Because of the complexity in ecology of the organisms living in the aquatic ecosystem as part of the food chain, the remarkable regional characteristics in ecosystems as observed for the differences in habitat and ecosystem between the Great Lakes in the United States and Lake Biwa in Japan and, in addition, the dif- ferent aquatic ecosystem to be protected depending on the culture, ideologies and values of the people in vari- ous regions, etc., it is not only difficult to make uniform assessments, but also the current situation is one in which there is a great variety in the methodology for evaluation taken by the agencies regulating pesticides Ecotoxicological Risk Assessment of Pesticides in Aquatic Ecosystems Sumitomo Chemical Co., Ltd. Environmental Health Science Laboratory Mitsugu MIYAMOTO Hitoshi TANAKA Toshiyuki KATAGI Ecotoxicological risk assessment of pesticides in aquatic ecosystems has become one of the most important areas of scientific pesticide evaluation. Sumitomo Chemical has been developing many pesticides in order to maintain a stable worldwide food supply, and we have been conducting high quality ecological risk assess- ments by using state-of-the-art techniques for the evaluation of our pesticides. In this article, the outline of the aquatic ecological risk assessment procedures in Japan, the USA and the EU are briefly summarized and some examples of sophisticated higher-tier ecotoxicological studies undertaken to demonstrate that our pesti- cides are benign to aquatic environment are introduced. This paper is translated from R&D Report, “SUMITOMO KAGAKU”, vol. 2008-I.
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1SUMITOMO KAGAKU 2008-I
Introduction
With the goal of providing food for the human race
as well as having a stable food supply at present and in
the future, agricultural chemicals (i.e. pesticides) are
being disseminated as economically effective methods
for preventing reduced yields in crops due to damage
by insects and weeds. The pesticides are roughly divid-
ed from their targets into insecticides which include
insect growth regulators for exterminating harmful
insects, fungicides for preventing and eliminating fungi
such as powdery mildew affecting the growth of plants,
and herbicides which include plant growth regulators
for preventing weeds, and each of them has a superior
efficacy for organisms that are harmful to crops. These
pesticides are intentionally applied outdoors to agricul-
tural land, so in addition to the efficacy of pesticides for
various diseases and insects that damage crops (bene-
fit), evaluations of their impact not only on the health of
farmers and consumers but also wild animals (risk) are
necessary in determining their usefulness as pesti-
cides. There is a long history of safety evaluations
based on various types of toxicity tests using mammals
from the standpoint of assuring the health of humans,
but there has been an increase in the awareness of
environmental protection recently, and evaluations of
the effects of pesticides on the environment, including
wild animals, have become indispensable for develop-
ment of new pesticides and maintaining the registra-
tion of existing chemicals already on the market. How-
ever, there is a wide variety of wild animal species to be
evaluated, and just among the vertebrates alone, there
are various types including mammals, birds, reptiles,
amphibians and fish. In addition, the diversity of their
ecology and shortage of information on life history of
some species make it very difficult to evaluate the safe-
ty for individual species. Incidentally, since the pesti-
cides that are applied to cultivated land are considered
to enter the hydrosphere of the rivers and lakes adja-
cent to the cultivated fields with the movement of air
and rain as they undergo various types of metabolism
and decomposition, the evaluation of the environmental
impacts of pesticides on the ecosystem of the hydros-
phere is one of the most important areas in evaluations
of safety. Because of the complexity in ecology of the
organisms living in the aquatic ecosystem as part of the
food chain, the remarkable regional characteristics in
ecosystems as observed for the differences in habitat
and ecosystem between the Great Lakes in the United
States and Lake Biwa in Japan and, in addition, the dif-
ferent aquatic ecosystem to be protected depending on
the culture, ideologies and values of the people in vari-
ous regions, etc., it is not only difficult to make uniform
assessments, but also the current situation is one in
which there is a great variety in the methodology for
evaluation taken by the agencies regulating pesticides
Ecotoxicological Risk Assessmentof Pesticides in AquaticEcosystems
Sumitomo Chemical Co., Ltd.
Environmental Health Science Laboratory
Mitsugu MIYAMOTO
Hitoshi TANAKA
Toshiyuki KATAGI
Ecotoxicological risk assessment of pesticides in aquatic ecosystems has become one of the most importantareas of scientific pesticide evaluation. Sumitomo Chemical has been developing many pesticides in order tomaintain a stable worldwide food supply, and we have been conducting high quality ecological risk assess-ments by using state-of-the-art techniques for the evaluation of our pesticides. In this article, the outline ofthe aquatic ecological risk assessment procedures in Japan, the USA and the EU are briefly summarized andsome examples of sophisticated higher-tier ecotoxicological studies undertaken to demonstrate that our pesti-cides are benign to aquatic environment are introduced.
This paper is translated from R&D Report, “SUMITOMO KAGAKU”, vol. 2008-I.
2SUMITOMO KAGAKU 2008-I
Ecotoxicological Risk Assessment of Pesticides in Aquatic Ecosystems
in various countries.
Sumitomo Chemical has been developing many pes-
ticides in order to maintain a stable worldwide food
supply, and we have been conducting high quality eco-
logical risk assessment by using state-of-the-art tech-
niques for the evaluation of our pesticides. In this arti-
cle, the outline of the aquatic ecological risk assess-
ment procedures in Japan, the USA and the EU are
briefly summarized and some examples of sophisticat-
ed higher-tier ecological studies undertaken to demon-
strate that our pesticides are benign to aquatic environ-
ments are introduced.
Environmental Assessments in the Hydros-
phere
1. Concept of assessing environmental impact
In addition to first describing the variety and charac-
teristics of the “natural environment” and “organisms”
that are the target of assessments of environmental
impact, we will give an overview of the “environmental
behavior of pesticides,” which is important for knowing
how organisms we are targeting are exposed to pesti-
cides or their degradation products and metabolites
generated in the natural environment. We will give a
simple introduction to the basic concept of environ-
mental assessment based on these.
(1) Natural environment and organisms
The natural environment, which is roughly divided
into the “hydrosphere,” “pedosphere (soil)” and
“atmosphere,” is formed of various ecosystems that
interact with each other in a complicated manner.
According to the Biodiversity Protocol,1) an ecosystem
is “a dynamic composite that forms a single functional
unit where a community of plants, animals and
microorganisms and the abiotic environment surround-
ing them interact”. In other words, the ecosystems we
are targeting are ones in which there are a wealth of
dynamic spatio-temporal changes due to physical (sun-
light, water temperature, etc.), chemical (nutrients,
trace metals, etc.) and geographical (climate, topogra-
phy, etc.) environmental factors intimately linked in the
complex interactions of the predation, prey, competi-
tion, parasitism, propagation, decomposition, etc., of
the various organisms. As can be seen from the exam-
ple of a schematic diagram of an ecological pyramid of
an aquatic community shown in Fig. 1, a food chain,
hierarchical (pyramid) structure and cycle of matter
are established. The interaction of the predation, prey,
competition, etc., of producers such as algae and a hier-
archy of consumers, which are known as crustaceans
and fish (primary consumers, secondary consumers,
higher predators, etc.) and decomposers such as bacte-
ria is woven here.
Furthermore, the number of species on the earth,
just with the presence of animals, is very large at one
million or more,2) and along with their being classified
in detail as in Table 1, there is a great variety in habi-
tats, lifecycles, lifestyles and reproductive strategies in
each species. For example, in terms of the mode of
reproduction, there is a division into asexual reproduc-
tion such as budding and division and sexual reproduc-
tion, and sexual reproduction may further divided into
Fig. 1 Typical ecological pyramid in an aquatic community
Solar power, nutrition (e.g. N, P)
predation
Top predator(e.g. large fish)
Secondary consumer(e.g. small fish, dragonfly )
Primary consumer(e.g. zooplankton)
Producer(e.g. algae)
Decomposer(e.g. bacteria)
interaction
Table 1 Taxonomic classification and variety of re-productive strategies of animals
Population (number of evaluated taxa)Phytoplankton (14)Periphyton (2) Macrophytes (1)Zooplankton (29)Macroinvertebrates (34)
CommunityPhytoplanktonOpen water invertebrateSubstrate associatedSediment dwellerEmergent insectTaxonomic Richness
Ecological evaluation including recoveryNOEAEC
200 ng/L30 ng/L12 ng/L6 ng/L3 ng/L1 ng/L
1 – 21 NOEC1 NOEC
1 – 51 – 5
NANANANANA
1 – 3
1 NOEC11
1 – 31 – 3
1 NOEC1 NOEC1 NOEC1 NOEC1 NOEC1 NOEC
X
111
1 – 21 NOEC
111111
111
1 NOEC1
111111
11111
111111
11111
111111
Effect Classification*
* : Effect classification was based on the EU guidance and summarized as follows : Class 1 : no effect ; Class 2 : slight effect ; Class 3 : short term effect ; Class 4 : long term effect with recovery ; Class 5 : irreversible long-term effect
11SUMITOMO KAGAKU 2008-I
Ecotoxicological Risk Assessment of Pesticides in Aquatic Ecosystems
tion (NOEAEC), which takes recovery into considera-
tion, was assessed at 30 ng/L.39)
2) Fish mesocosm study
The test system can be set up in a similar manner to
the test system for invertebrates, but based on the vari-
ous considerations, such as the level of fish predation
pressure, the size of the biomass, maintaining the qual-
ity and other organisms and methods of observation, a
larger test system was used, housing cages set up and
the design made for contact between the bottom sedi-
ment and fish in long-term exposure (Fig. 9 and 10).
Assessment of acute ecological effects was carried
out by exposing fish separated out in cages to the
water system. On the other hand, assessment of long-
term effects was carried out with the cage bottoms
removed envisioning contact (feeding activity) of the
fish with the bottom where the substance being tested
was adsorbed. Furthermore, the supplemental feeding
was carried out using food organisms (benthic worms
and midges, prepared in multiple small containers) that
had been exposed to esfenvalerate separately, and an
assessment test system closer to reality was construct-
ed by considering exposure throughout the food chain.
Furthermore, to examine the effects on fish migrating
from unexposed areas, cages containing the fish were
added after treatment with the substance being tested,
and mitigation of the ecological effects were verified.
As is shown in Fig. 11, the acute LC50 value for rain-
bow trout in the mesocosm test system was approxi-
mately 5 times higher than the results from the lower
tier tests at 550 ng/L, and the effects on the fish that
were added after distribution clearly dropped all with
the passage of time. It was possible to demonstrate the
capacity for recovery from the ecological effects for the
populations including migrating fish.
In addition, in the tests assessing the long-term func-
Fig. 9 Photograph of the test system (fish meso-cosm)
Fig. 10 Schematic view of the enclosure (fish me-socosm)
Day 2-6 Day 4-8 Day 6-10Day 1-5
Stainless Steel Enclosure (3m3 size)
Fish Cage
AcuteTest
Chronic Test•Bottomless cage•Feeding of exposed food organisms
* : Effect classification was based on the EU guidance and summarized as follows :Class 1 : no effect ; Class 2 : slight effect ; Class 3 : short term effect ; Class 4 : long term effect with recovery ; Class 5 : irreversible long-term effect
16SUMITOMO KAGAKU 2008-I
Ecotoxicological Risk Assessment of Pesticides in Aquatic Ecosystems
ious areas starting with the OECD, and the various
methods proposed in AEDG,16) HARAP,8)
ECOFRAM,19) EUPRA,45) the “Registration Withhold-
ing Standards of Agricultural Chemicals concerning
Prevention of Damage to Aquatic Animals and Plants”
report from the Ministry of the Environment Govern-
ment of Japan,11) the FOCUS Working Group report24)
and various other reports, etc., for which use is still
insufficient, that is probabilistic methods, advanced
region specific simulations, meta-population modeling,
test methods for simulating flow-through microcosm,
etc. In addition, there are expectations for further
investigations in the future into the use of various
QSAR toxicity prediction methods, genomics tech-
niques that are used in pharmaceutical development
and others that will be useful in the future. We are con-
tinuing discussions, applications and collection of
knowledge about the microcosm and mesocosm test
techniques introduced here, and moving forward,
progress toward greater know-how, and refined assess-
ments by building up technology are desirable. We
would like to confirm the safety of Sumitomo Chemi-
cal’s pesticides in the ecosystems and carry out devel-
opment of pesticides that are more environmentally
benign by driving these new technologies forward.
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18SUMITOMO KAGAKU 2008-I
Ecotoxicological Risk Assessment of Pesticides in Aquatic Ecosystems
P R O F I L E
Mitsugu MIYAMOTO
Sumitomo Chemical Co., Ltd.Environmental Health Science LaboratorySenior Research Associate
Toshiyuki KATAGI
Sumitomo Chemical Co., Ltd.Environmental Health Science LaboratoryGroup ManagerPh. D.
Hitoshi TANAKA
Sumitomo Chemical Co., Ltd.Environmental Health Science LaboratoryResearch AssociatePh. D.